Acrylonitrile interpolymers



United States Patent 3,325,458 ACRYLONITRE E INTERPOLYMERS Chung Sul Kim, Bellingham, Wash, and Linda M. Wick, Warrensville Heights, Ohio, assignors to The Standard Oil Company, Cleveland, Ohio, a corporation of Ohio No Drawing. Filed Nov. 29, 1965, fies. No. 510,371 6 Claims. (Cl. 260--80.5)

This is a continuation-in-part application of our copending US. patent application Ser. No. 273,840, filed Apr. 18, 196-3 and now abandoned.

This invention relates to novel interpolymers of an alpha, beta-olefinically unsaturated nitrile, a 2-alkyl-lolefin and a lower acrylic ester and more particularly pertains to novel resinous interpolymers having excellent heat distortion temperatures and thermal stability as well as excellent uniformity, homogeneity and clarity, composed of an alpha, beta-olefinically unsaturated mononitrile having from 3 to 5 carbon atoms, a 2-alkyl-1-olefin hydrocarbon having from 6 to 12 carbon atoms and a lower alkyl acrylic ester containing from 4 to 6 carbon atoms.

The copolymerization of an alpha, beta-olefinically unsaturated nitrile, such as acrylonitrile, with a Z-methyl-lolefin is disclosed in US. Patents Nos. 2,621,170 and 2,749,330. The interpolymerization of acrylonitrile, isobutylene and methylene methacrylate is described in US. Patent No. 2,537,626. However, there is believed to be no prior disclosure of the particular three component interpolymers embodied herein.

The present invention is concerned with the resinous interpolymers resulting from the interpolymerization of three monomers exemplified by the preferred acrylonitrile, alpha-diisobutene (2,4,4-trimethyl pentene-l) and methyl acrylate.

Other alpha, beta-olefinically unsaturated mononitriles which are useful in the present invention include methacrylonitrile, ethacrylonitrile, alpha-chloroacrylonitrile, crotonic nitrile and the like.

Other 2-alkyl-l-olefin hydrocarbons which are useful in the present invention include Z-methyl pentene-l, 2- methyl hexene-l, alpha-triisobutene and the like.

Other lower alkyl esters of acrylic acid which are useful in the present invention include ethyl .acrylate and propyl acrylate and the like.

Preferred in the present invention are the resinous interpolymers resulting from the interpolymerization of from 45 to 70% by weight of the alpha, beta-olefinically unsaturated nitrile, from 20 to 40% by weight of the 2- a1kyl-1-olefinic hydrocarbon and from 5 to 25% by weight of the lower alkyl acrylic ester. In the foregoing preferred ranges of monomers it is to be understood that in any given interpolymerization reaction the sum of the weight percentages of the three monomers will always be 100% by weight.

The primary technical advantage of the present invention is concerned with the surprising discovery that the incorporation of a -2-alkyl-l-olefinic hydrocarbon as a third comonomer into the known polymerizable mixture of alpha, beta-olefinically unsaturated nitrile and lower alkyl acrylic es-ter results in polymeric products having essentially similar flexural strengths but significantly higher heat distortion temperatures and excellent uniformity, homogeneity and clarity in the consolidated or molded form. This improvement in heat distortion temperature changes, for instance, the unsatisfactory acrylonitrilemethyl acry-late copolyrner resin to a very satisfactory acrylonitrile-alpha-diisobutene-methyl acrylate terpolymer molding resin.

There are, in addition to the foregoing, other technical and economic advantages associated with the composi- 3,325,458 Patented June 13, 1967 tions of this invention. One of the prominent drawbacks of many acrylonitrile polymers has been their pronounced tendency to discolor at elevated temperatures. The causal basis of this deficiency is ascribed to the formation of conjugated carbon-nitrogen chains by the interaction of the pendant nitrile groups on the acrylonitrile polymer. One method suggested for controlling this deficiency is to modify the polymer by incorporating another monomer, possibly an unreactive monomer, into the polymer so that the interaction of neighboring pendant nitrile groups is suppressed or stopped entirely. Hydrocarbon olefins might do this, but the usual hydrocarbon monomers such as ethylene, propylene and isobutylene show little or no tendency to copolymerize uniformly with acrylonitrile. It is disclosed in US. Patent No. 2,537,146, for instance, that it is preferred in the copolymerization of isobutylene with acrylonitrile in order to get appreciable amounts of isobutylene into the polymer to employ isobutylene in preponderant amounts, say, in the ratio of two and a half parts or more to one part of acrylonitrile. It is indeed unexpected that 2-alkyl-1-olefinic hydrocarbons such as 2,4,4-trimethyl pentene-l interpolymerize readily with acrylonitrile and a lower alkyl acrylic ester with the result-ant improvement in thermal properties as well as a decided improvement in the transparency in the consolidated or molded form.

A concurrent economic advantage displayed by the compositions of this invention arises from the fact that the hydrocarbon olefins are cheaper than most other monomers and their utilization reduces the materials cost of the resultant polymeric resin. In the case of the use of a higher molecular weight olefin, such as alpha-diisobutene, an additional economic benefit arises. Because the molar reactivity ratios of monomers are dependent primarily upon their functional groups and not upon their molecu lar weights, a proportionately greater mass fraction of the final polymeric resin is derived from the hydrocarbon monomer when higher molecular weight olefins are used.

An economic advantage is also connected to the particular higher olefin, alpha-diisobutene, which is preferred in this invention. One of the reasons why the higher monoolefins have not been used more extensively as comonomers is the difiiculty in purification, particularly for the higher molecular Weight mono-olefins. Hydrocarbon olefins such as alpha-diisobutene are easily and economically prepared. Alpha-diisobutene, for instance, is conveniently prepared by the acid catalyzed dimerization of isobutene. Although a mixture of alpha-diisobutene (2,4,4- trimethyl pentene-l) and beta-diisobutene (2,4,4-trimet-hyl pentene-2) is formed in the dimerization of isobutene, the alpha-diisobutene constitutes about of the product, and beta-diisobutene is completely unreactive in the present copolymerization reaction. Thus the commercial mixture may be utilized directly in the inst-ant process without any further purification step which necessarily would add to the cost of the monomer. The diisobutene mixture is very inexpensive and readily available.

The interpolymers of this invention can be prepared by bulk, solution or emulsion polymerization techniques although bulk and emulsion polymerizations are preferred and emulsion polymerization is most preferred.

As medium for the emulsion polymerizations of this invention there may be employed water with or without emulsifying agents. Suitable emulsifying agents include organic alkali metal sulfates and sulfonates such as the higher fatty sulfates and sulfonates; higher fatty esters, amides and ethers of groups bearing sulfate and sulfonic groups; aromatic and alkylated aromatic sulfonates, and the like. There also may be employed the fatty acid alkali metal soaps; metal salts of organic phosphate esters; cationic surface active agents such as the fatty amines and amid-o-amines; and non-ionic surface active agents such as the condensed glycols and polyvinyl alcohol. When it is desired to employ an emulsifier in the instant polymerization process, the aqueous media may contain bomb or other suitable vessel, and mounted in an appropriate tumbling or shaking apparatus. Large scale preparations are preferably carried out in stationary autoclaves provided with suitable rotary agitating means in upwards of about 0.5% and preferably from 1 to 3% of 5 the interior thereof. the emulsifier or emulsifiers, depending upon the eifec- The interpolymers of this invention are highly suitable tiveness of the specific emulsifying agents used, and also for the manufacture of films, fibers and are particularly upon the desired state of the final product; thus, if it is useful as molding resins in the manufacture of transdesired that the final product shall be a stable latex, parent articles. more emulsifier will be employed than if a granular or The compositions and processes of this invention are lumpy product is acceptable. further illustrated in the following examples wherein the In general, a sufficient amount of the aqueous medium amounts of ingredients are expressed as parts by weight is employed to provide a conveniently workable polymerunless otherwise indicated. ization mass, this quantity being upwards of 75%, and Example 1 preferably about 100%, based on the weight of monomers, 2 0% or more may be employed, but m usually be Experimentaf samples of compositions falling within found unnecessary and wasteful of space in the reaction the eeope thls lhvehhoh and e Propertles of the equipment sulting plastic polymers-are shown in Table I. The 70/ 30 Any of the usual tree radical inititators may be incop copolymer of acrylonitrile and methyl acrylate is included porated into the polymerization mass to promote the 0 In Table I for eomharahve Purposes reaction, such catalysts being exemplified by, but not AS w be noted In the e e eomposmoms of h limited to, hydrogen peroxide, per-salts, such as potassium lhvehhoh e be Prepared elther 1h bulk or emulslon persulfate, sodium persulfate, ammonium persulf-ate, orpelymenzahoh- Expenmehtahy, both h and h genie acid peroxides Sueh as benzoyl pemxide and pen sion polymerizations were run overnight in sealed eight acetic acid, azo initiators, such as azodiisobutyronitrile Ounce homes In a hltrogehahhosphere at 60 and similar materials more fully disclosed in US. Patent In the ease h h f e the Products: were No. 2,471,959; and other similar catalysts including the recovered y pre ipitation from dimethyl fo rrn amide or so-called redox catalysts such as a combination of an methyl ethyl ketohe, whleh they were e e h and oxygen-yielding substance and a reducing agent exemplipartially dissolved. The amount of aorylonitrile in the fied by potassium persulfate and Sodium bisulfite and polymeric products was determined by nitrogen analysis, similar combinations such as the types disclosed in U.S. and the PreSehee of h of the mohofhehs m the Poly Patent No. 2,486,241 and British Patent No. 586,881 mers was establlshed y infrared analysis. and others well known to those skilled in the art. The h the Polymers e dned m a Vacuum Oven amount of catalysts used may vary from about 0.1 to 5% Overhlght, and was eomlfressloh molded at by Weight based on the Weight Of monomers, the greater 4000 pm. The mechanical properties were determined quantities resulting in higher yields in any given time, oh uhahhealed h at the expense of some reduction in average molecular h the followlhgutable AN deslgnates aerylonltl'lle, D13 Weight of the produet. designates alpha-d-iisobutene, MA designates methyl acryl- The interpolymerizations of this invention are prefer- AIBN deslghates azohlslsohutyrohlmle M e ably conducted in the substantial absence of molecular 40 hates t'dodeeyl mereaptah the ASTM heat dlsfomoh oxygen and they may be carried out at temperatures temperatures was each determined under a 66 p.s.1. load. varying from about 30 C. to about 80 C. or higher. At A typleal emulsloh reelpe 1S as follows: the lower temperatures, the reaction generally proceeds P3115 more slowly with the formation of higher molecular e e monomer 100 weight polymers and conversely, at higher temperatures Dlshhed water 167 the reaction proceeds rapidly with the formation of poly- GAFAC RE 610 1 (emulslher) mers of somewhat lower molecular weight. A good balmereaptah ance between economy of operation and quality of prod- Potasslum persulfate not will be found in the preferred range of from about iw is a mixture of R-O(CH CH2O)..PO.MZ and 40 to 70 C. Under these conditions the reaction will g 1;g0 I({ i s 2q n ;1 l T)0hI;|iglgigllwhereinTI/(51S alttlltngfr of front proceed substantially to its maximum conversion (usualn i i-ou and ii is i.f ;;f, e e i gg ly 70% or more) in approximately 8 to 16 hours. Th which composition is sold by the General Aniline and Film unreacted monomers then remaining may be suitably re- Corp covered and recycled. The resulting latices were coagulated with aluminum sul- The polymerization process of this invention may be fate and the coagulated polymers were washed six times carried out in various types of apparatus. The polymerwith water and were then dried prior to molding. The iza-tion may be carried out at atmospheric, subatmospheric molded polymers listed in Table I which are Within the or superatmospheric pressures. 'For the production of scope of this invention were all transparent and appeared small lots of resin, the ingredients may be sealed up in a to be of a uniform, homogenous composition.

TABLE I Monomer Ratio Percent ASTM Heat Flcxnral AN in Polymerization Method Percent Distortion Strength, Sh0reD AN DiB MA Polymer Yield Tempeature, p.s.i. Haxdness 55 27 18 62. 2 0.40 g. AIBN, Bulk at C 28 66 13, 300 g 55 27 18 63.0 o.27 0 1 isi0i, 0.374 g. t-DM, Emulsion 79 71 17, 300 90 64 27 9 72. 5 0.2305. Kisiog, 0.374 g. t-DM, Emulsion 7s 80 18,700 37 1o a0 70 0.27tU6gd K2 szOs, 0.374 g. t-DM, Emulsion 60 21, 000

45 55 0.f5 l 2zOt, 0.02 g. tDM, Emulsion 100 01 12, 000 89 45 30 25 0.25 g. KZSQO 0.62 g. t-DM, Emulsion 70.7 75.5 12, 200

7o 25 5 0.4% m'siot, 0.62 g. t-DM, Emulsion 78.2 100.5 go

at 60 C.

Example 11 The procedure of Example I was followed employing the emulsion recipe:

The polymerizations were carried out under nitrogen in eight ounce bottles. The total polymerization time was 18.5 hours at a temperature of 60 C. The resulting latices were coagulated with aluminum sulfate and the polymers were washed six times with water and were then dried before molding. All test bars were compression molded at 150 C. and 4000 p.s.i.g. The results of these polymerizations and physical testing are given in Table II. In Table II the term AN means acrylonitrile, 2-MP means 2-methyl-1-pentene, MA means methyl acrylate, DiB means diisobutene, MAN means rnetharylonitrile, EA means ethyl acrylate. The test bars of the molded polymers given in Table II were all transparent and appeared to be of a uniform, homogeneous composition.

A prior art polymer which is outside the scope of the present claims was prepared from isobutene, acrylonitrile and methyl methacrylate according to the procedure given in Example II of US. Patent No. 2,537,626. The polymer was washed and dried and molded in the same manner (150 C., 4000 p.s.i.) as that for the polymers above. The molded bar was found to have an ASTM heat distortion temperature of 64 C. at 66 p.s.i., a flexural strength of 11,900 p.s.i. and it was opaque, apparently composed of a non-uniform, non-homogeneous mixture We claim:

1. A resinous interpolymer having excellent uniformity, homogeneity and clarity in the molded form resulting from the polymerization for from about 8 to 16 hours to a conversion of at least 7 0% in an aqueous medium of a monomer mixture of from 45 to 70% by weight of an alpha, beta-olefinically unsatutrated mononitrile having from 3 to 5 carbon atoms, from 20 to by weight of a 2-alky1-1-olefin hydrocarbon having from 6 to 12 carbon atoms and from 5 to 25% by weight of a lower acrylic ester containing from 4 to 6 carbon atoms in the presence of from 0.1 to 5% by weight based on the combined weights of monomers of a free radical initiator.

2. The interpolyme r of claim 1 wherein the alpha, betaolefinically unsaturated mononitrile is acrylonitrile.

3. The interpolymer of claim 2 wherein the 2-alkyl-1- olefin is alpha-diisobutene.

4. The interpolymer of claim 3 wherein the lower acrylic ester is methyl aorylate.

5. The process comprising interpolymerizing for *from about 8 to 16 hours in an aqueous medium a monomer mixture of from to by weight of an alpha, betaolefinically unsaturated nitrile having from 3 to 5 carbon atoms, from 20 to 40% by weight of a 2-alkyl-1- olefin hydrocarbon having from 6 to 12 carbon atoms and from 5 to 25% by weight of a lower acrylic ester containing from 4 to 6 carbon atoms at a temperature: of from 30 to 80 C. in the presence of from 0.1 to 5% by weight based on the combined weight of monomers of a free radical initiator said aqueous medium being present in at least about by weight based on the weight of monomers.

6. The process of claim 5 carried out in the substanof polymers. 35 tial absence of molecular oxygen.

TABLE II ASTM Heat Flexural Monomer Ratio Percent Distortion Strength, Shore D Yield Tempeature, p.s.i. Hardness 55AN/27 2-MP/18MA 82. 1 73. 5 14, 300 55AN/27DiB/18EA 78.6 78. 5 9, 89 55MAN/27DiB/18MA 64. 7 96. 0 13, 200 89 References Cited UNITED STATES PATENTS 2,537,626 1/1951 Eberly et al. 260-80.5 X 2,833,746 5/1958 Haefner 260-80.5 X

JOSEPH L. SCHOFER, Primary Examiner. W. HOOVER, Assistant Examiner. 

1. A RESINOUS INTERPOLYMER HAVING EXCELLENT UNIFORMITY, HOMOGENEITY AND CLARITY IN THE MOLDED FORM RESULTING FROM THE POLYMERIZATION FOR FROM ABOUT 8 TO 16 HOURS TO A CONVERSION OF AT LEAST 70% IN AN AQUEOUS MEDIUM OF A MONOMER MIXTURE OF FROM 45 TO 70% BY WEIGHT OF AN ALPHA, BETA-OLEFINICALLY UNSATURATED MONONITRILE HAVING FORM 3 TO 5 CARBON ATOMS, FROM 20 TO 40% BY WEIGHT OF A 2-ALKYL-1-OLEFIN HYDROCARBON HAVING FROM 6 TO 12 CARBON ATOMS AND FROM 5 TO 25% BY WEIGHT OF A LOWER ACRYLIC ESTER CONTAINING FROM 4 TO 6 CARBON ATOMS IN THE PRESENCE OF FROM 0.1 TO 5% BY WEIGHT BASED ON THE COMBINED WEIGHTS OF MONOMERS OF A FREE RADICAL INITIATOR. 